Well, i meant precisely the city loops which aren't multihomed, and that's what customers are using to access telco facilities. I.e. POTS customers (and their PBXes) aren't multihomed in the sense used in the discussion. The better term for telcos are doing for reliability between switch sites is called "standby", which is *not* the same as multihoming with adaptive routing. The point was that high reliability may be achieved w/o tricky things like adaptive routing, --vadim

From sdenny@red.hex.net Mon Jan 29 21:14:22 1996 Received: from tiny.sprintlink.net (tiny.sprintlink.net [199.0.55.90]) by titan.sprintlink.net (8.6.9/8.6.9) with ESMTP id VAA09936 for <avg@titan.sprintlink.net>; Mon, 29 Jan 1996 21:14:21 -0500 Received: from red.hex.net (sdenny@red.hex.net [198.175.15.226]) by tiny.sprintlink.net (8.6.9/8.6.9) with ESMTP id VAA14645 for <avg@sprint.net>; Mon, 29 Jan 1996 21:14:11 -0500 Received: (from sdenny@localhost) by red.hex.net (8.6.10/8.6.10) id UAA02836; Mon, 29 Jan 1996 20:14:00 -0600 Message-Id: <199601300214.UAA02836@red.hex.net> From: sdenny@red.hex.net (Stephen Denny) Date: Mon, 29 Jan 1996 20:14:00 -0600 In-Reply-To: Vadim Antonov <avg@sprint.net> "Re: Policy Statement on Address Space Allocations" (Jan 29, 4:19pm) X-Mailer: Mail User's Shell (7.2.5 10/14/92) To: Vadim Antonov <avg@sprint.net> Subject: Re: Policy Statement on Address Space Allocations Cc: nanog@merit.edu, sdenny@red.hex.net Status: R

On Jan 29, 4:19pm, Vadim Antonov wrote:

Note that regular telephone service does not generally employ multihoming and dynamic adaptive routing, but has a lot better reliability. Something to think about.

}-- End of excerpt from Vadim Antonov Regular telephone service is indeed generally multihomed except for the final loop from the central office. SS7 is a major pain partly because of the multiple routes it supports. - Multiple links in linksets (partly for capacity, partly for reliability) - Multiple linksets in routesets, where each linkset terminates on a different node Typically the CO is "multihomed" to two mated STPs for signaling traffic, and user traffic is routed through multiple tandems based on load, availability, cost and destination. Of course SCPs are also deployed in pairs. All this is in addition to the redundancy built into each piece of equipment, or the underlying transport (e.g. sonet). Of course none of this stuff comes for the price of a Cisco router either. What *is* true is that the telephone network is more or less a static network in terms of routing (although becoming less so). It would be big news indeed if a new CO just popped onto the network and started "announcing" itself! This "static routing" idea makes for ultimate control and predictability even with multiple routes. Stephen -- --------------------------------------------------- Stephen Denny sdenny@hex.net Member of the Technical Staff, Hex.Net Superhighway